Although bicycles have been widely used for a long period of time, recent years have witnessed a widespread increase in the popularity of bicycling as a healthful and enjoyable recreational activity, as well as a renewed awareness of their utility as an inexpensive means of individualized local transportation. As a concommitant thereto, there has been a renewed emphasis on the utilization of multi-speed transmission systems for bicycles to enhance their operational efficiency over various types of terrain and to accommodate the ever expanding differences in the state of physical conditioning and capabilities of the users thereof. Although the patented art is replete with many different types of suggested multi-speed transmission systems, economic realities and practical considerations have apparently limited widespread commercial usage to two, three and five speed transmissions located within the rear wheel hub and to the widely utilized ten speed transmissions of the "derailleur" type, all of which are normally operable in response to a cable connected and manually manipulatable shift lever and which require a hand operated brake system. Also used, but to a lesser extent, are the more complicated drive pedal manipulative types of rear wheel hub multi-speed transmissions that are compatible with coaster brake drive systems, as for example, the Fichtel and Sachs AG "Torpedo" transmissions.
Among the many suggested bicycle transmission systems disclosed in the patented art are numerous disclosures of coaster brake compatible, rear wheel hub transmissions activated by reverse drive pedal rotation, as exemplified by the patents of Schwerdhofer (for example--U.S. Pat. Nos. 3,648,809, 3,270,589, 3,200,699, 3,180,181, 3,147,641); Hood (for example--U.S. Pat. Nos. 3,022,682, 2,993,575, 2,982,384, 3,972,908, 2,940,339) and Gleasman (for example--U.S. Pat. Nos. 3,354,750, 2,993,389, 2,903,913, 2,914,152). Other suggested and exemplary expedients for rear wheel hub transmission systems include reverse drive pedal actuatable epicyclic gear systems as disclosed in U.S. Pat. Nos. 3,351,165, 3,433,097, 3,803,947 and 3,726,156 and manually selectable rear wheel hub transmissions as embodied in U.S. Pat. Nos. 3,653,273 and 3,886,811.
Rear wheel hub multi-speed transmission systems, and particularly those that are coaster brake compatible, are of relatively complicated construction with diminutively sized components dictated by the limited available space. As such and because of the wheel diameter lever arm inherent in rear wheel hub located multi-speed transmissions, such are unduly subject to damage through normal, much less abusive, use and the repair thereof is usually both relatively difficult and expensive. Even the simpler rear wheel hub multi-speed transmission systems that are widely employed in hand brakeable bicycles, such as the Sturmey-Archer three speed and "derailleur" type multi-speed transmissions, are subject to hub component and gear shift cable damage that necessitate relatively expensive repairs as well as requiring diversion of the rider's attention when manual shifting is to be effected.
Early expedients for proposed utilization of the drive pedal hub area as a situs for multi-speed transmission components for bicycles are illustrated in U.S. Pat. Nos. 2,047,174 and 2,165,201 and in Swiss Patent No. 183,921. In each of these patents an in-line type of multi-speed transmission is employed, apparently sized to be contained within the drive pedal hub. Selective gear engagement was therein effected by spring biased radial pawl displacement induced by a control cam element disposed within an axial bore within the drive pedal shaft and operable in response to reverse rotation of the pedal drive shaft. Such approach is also characterized by diminutively sized components unduly subject to damage in a high stress location.
Recent years have witnessed a refocussing of attention upon the drive pedal hub as a suitable situs for multispeed transmission components for bicycles. One suggested expedient includes the utilization of a planetary gear system adjacent to the drive pedal hub that is compatible with a rear wheel hub coaster brake assembly but which requires manual operation of an external gear shift lever to effect shifting. Such a suggested construction is disclosed in the Shea U.S. Pat. Nos. 3,727,484, 3,766,805 and 3,842,691. Other suggested expedients include impact responsive shifting mechanisms, and manually controllable variations in the main drive pedal sprocket diameter. Illustrative of such expedients are U.S. Pat. Nos. 2,600,586, 1,608,141 and 3,506,100 and various publications such as Design News of Dec. 16, 1974 (pp. 46-7) and Product Engineering of June 1973 (p. 13).